Effect units have been considered essential tools for electric guitarists ever since The Shadows used a Watkins Copicat in the early days of rock ‘n’ roll. But keyboard players also use pedals to alter the sound of their instruments and explore sonic boundaries, and the sound of some keyboard and pedal combinations are truly inseparable from the songs in which they are featured.

Here’s a look at six of the most famous songs featuring keyboards processed through effect pedals.

Led Zeppelin - “No Quarter”

Studio: Hohner Electra-Piano, EMS VCS3, Moog Taurus

Live: Fender Rhodes Mark I Stage 73, Maestro PS-1A Phase Shifter

Led Zeppelin’s bassist and multi-instrumentalist John Paul Jones recorded the underwater sounds of “No Quarter” from their 1973 album Houses of the Holy by running a Hohner Electra-Piano through the filter of a EMS VCS3 synthesizer and using the VCS3’s sine-wave LFO to create a wobbly effect. He also played the accompanying bass — in real time — by using the foot pedals of the first version of the Moog Taurus analog bass synthesizer. To recreate this rippling effect live, however, Jones ran his Fender Rhodes Mark I Stage 73 electric piano through a Maestro PS-1A Phase Shifter pedal, which was designed by Oberheim Electronics before they started making their own analog synthesizers.

Supertramp - “The Logical Song”

Wurlitzer 200A, Boss CE-1 Chorus Ensemble

Roger Hodgson normally recorded his Wurlitzer 200A electric piano through a Roland Jazz Chorus amplifier. But when Hodgson was recording the keyboard part for “The Logical Song” on Supertramp’s 1979 album Breakfast in America, he fed the output of his Wurlitzer through a DI and then split the signal to a Boss CE-1 Chorus Ensemble pedal to achieve a semi-modulated effect. The Boss CE-1 first was made in 1976 and was based on the chorus circuit of the Roland JC-120 Jazz Chorus amplifier, making it a natural choice for Hodgson.

Stevie Wonder - “Higher Ground”

Hohner Clavinet, Mu-Tron III Envelope Filter

Stevie Wonder is perhaps the most well-known Hohner Clavinet player, and the funky sound he popularized with it is best captured in “Higher Ground” from his 1973 album Innervisions. Wonder ran his Clavinet through a Mu-Tron III Envelope Filter pedal, creating an auto-wah sound that has influenced almost every Clavinet player ever since. The Mu-Tron III was the first envelope filter effects pedal ever made, and was modeled after the envelope filter of a synthesizer that the Mu-Tron’s designer Mike Beigel was making for the Guild Guitar Company. Beigel found the sound of the envelope-controlled filter to be more musical than other synthesizer circuits, such as ring modulators, and built an effects pedal to house his filter design.

Daft Punk - “Rollin’ & Scratchin’”

Roland Juno-106, Boss MT-2 Metal Zone

On their debut 1997 album Homework, Daft Punk frequently obtained a squelchy sound from their analog synths by overdriving their filters, such as the sound of the filters of the Korg MS-20 and Roland TB-303 used in “Da Funk.” However, for the song “Rollin’ & Scratchin’” on the same album, Daft Punk opted for the more distorted sound of a Roland Juno-106 analog synthesizer run through a Boss MT-2 Metal Zone pedal. They achieved this effect by slowly increasing the cutoff frequency of the Juno-106’s lowpass filter, with the resonance and noise sliders set to the maximum setting. This track was influenced by hardcore punk, and Daft Punk certainly achieved a similarly abrasive sound with this combination.

Jean Michel Jarre - “Oxygène Part IV”

Eminent 310 Unique, Electro-Harmonix Small Stone Phase Shifter

Photo credit: Spheremusic

Electronic musician Jean Michel Jarre used the unassuming polyphonic string synthesizer section of the Eminent 310 Unique electronic organ for almost all of the tracks on his 1976 album Oxygène. Working in the kitchen of his apartment with an eight-track recorder and his collection of analog synths, Jarre ran the Eminent 310’s string section through an Electro-Harmonix Small Stone Phase Shifter pedal; this effect can be heard most prominently on “Oxygène Part IV.” Jarre would go on to use the Eminent 310’s string section on his subsequent 1978 album Équinoxe.

Rush - “2112 (Part I: Overture)”

ARP Odyssey, Echoplex

Rather than try to tone down their sound after the commercial disappointment of their 1975 album Caress of Steel, Rush instead decided to experiment further with their follow-up 1976 album 2112, which proved to be a major success. The titular song opens with an overture to set the futuristic mood, and Rush used an ARP Odyssey analog synthesizer through an Echoplex tape delay unit, then a popular choice for delay sounds on guitar, to create the sci-fi noises and atmosphere of one of their most famous songs. The ARP Odyssey was played by Hugh Syme, the graphic designer who created Rush’s “Starman” logo as well as multiple Rush album covers, and the resulting sounds were assembled as a collage during mixing. This song marks the first time that Rush used a synthesizer on their albums, which would later become a mainstay of their sound.